Mirrored ceiling and wall surfaces are decoratively appealing, but prior to my U.S. Pat. No. 4,990,407 ('407) they presented structural and construction problems. As noted in that patent, if the mirror is to be glass, as is generally preferred, weight is a significant disadvantage, particularly in ceilings where it is difficult to handle large glass panels during installation and difficult to provide adequate structural support. Smaller glass mirrors, in the form or size of tiles, reduce the weight problem of each individual piece, but at least two significant problems remain. First, glass mirrors are not good acoustical absorbers, and therefore yield higher than necessary sound levels where used. Second, glass mirrors generally crack under heat and heretofore have been unacceptable where fire-resistant construction is desirable.
Another important objective of my '407 patent is personal safety. Conventional glass mirror installed in direct hung gridwork presents a possible safety hazard if impacted by a mop frame or other implement. In glass industry usage, a shatter-resistant mirror is the term used when a vinyl or other supporting sheet is adhesively secured to the back surface of a mirror, but such a structure helps to prevent shards of glass from falling from the mirror more than preventing the glass from shattering.
The overriding purpose of a mirror tile is decorative and my invention in my '407 patent made mirror tiles constructed of glass safe and practical. As commercially sold under the names Image-Safe.RTM., Tru-Mirror.RTM., and Island Reflections.TM., trademarks of Inter-County Building Materials Corp. of Deer Park, Long Island, N.Y., such tiles have been approved under building codes and have received Underwriters Laboratories Inc. (U.L..RTM.) approval.
Notwithstanding the purpose of my prior invention to make glass tiles safer (resisting breakage but if accidentally broken, the glass fragments remain in place), there is decorative purpose in having glass mirror tiles which are intentionally cracked. There is great visual beauty in a well-silvered glass mirror which is intentionally cracked or crazed throughout. My U.S. Pat. No. 5,277,952 ('952) provides a structure and method of making such tiles, and providing them with adequate protection when installed.
The invention of my '952 patent has a broader use than the specific purpose above described. In its broad principle, the invention provides a decorative cracked glass laminate in various forms such as tiles, panels, sheets, plates, veneers and in situ applications. The intermediate layer of the laminate is a sheet of tempered glass mirror. This intermediate layer is laminated between a supportive or protective backing such as a fiberboard panel, and an outer (front) transparent sheet, e.g., a sheet of annealed glass. The intermediate tempered glass mirror is caused to crack from edge to edge by cutting into one edge, as by a rotating diamond-tipped blade. The resulting laminate has actually cracked glass sealed behind an intact glass front and may be used as a ceiling tile, a floor tile, a wall decoration, a table or counter top, and various other applications.
The invention of my '952 patent accordingly provides a mirror construction which combines the visual advantages of an intentionally cracked glass mirror (distortionless reflected images, high resistance to discoloration due to aging or exposure to light or atmospheric attack) with none of the safety disadvantages of a conventional installation of glass and with high degrees of fire-resistance and acoustical absorption, in sizes and shapes adopted for ease of shipping, handling and installation. However, adhesives used to bond the outer glass cover to the glass mirror are limited in that they must be transparent to permit the cracked glass mirror image to be clearly seen without loss of clarity, both initially and over time and exposure. Included among Transparent adhesives disclosed in my '952 patent are those made of polyvinylbuterol (PVB). There are circumstances in which use of PVB adhesives are restricted or are undesirable.